In DC input devices, where is the load switched for 'Active High' versus 'Active Low' operation?

In DC input devices, where is the load switched for 'Active High' versus 'Active Low' operation?

• A. High side (source) or low side (ground)
• B. Voltage threshold
• C. Signal frequency
• D. Polarity of the sense

Answer: (A)

When a DC input is described as Active High, the input is considered on when the signal at the input line is at a higher voltage than ground, so the internal switch is placed on the high side (source). This means the load is connected to the supply through the switch when the external device drives the line high. When the input is Active Low, the input is on when the line is pulled toward ground, so the switch is on the low side (ground). The load is then connected to ground through the switch when the external device drives a low level. The other options don’t describe where the switching happens—they relate to when the input changes state or other signal characteristics, not which side of the circuit the switch sits on.

When a DC input is described as Active High, the input is considered on when the signal at the input line is at a higher voltage than ground, so the internal switch is placed on the high side (source). This means the load is connected to the supply through the switch when the external device drives the line high. When the input is Active Low, the input is on when the line is pulled toward ground, so the switch is on the low side (ground). The load is then connected to ground through the switch when the external device drives a low level. The other options don’t describe where the switching happens—they relate to when the input changes state or other signal characteristics, not which side of the circuit the switch sits on.